Encephalitozoon hellem is an intracellular, single-celled parasite that causes ocular, respiratory and systemic disease in immunocompromised humans. This microsporidian has been identified in several psittacine pet birds as subclinical as well as renal and fatal intestinal infections. The purposes of this study are to discover the extent to which pet birds function as reservoirs for this infection and whether zoonotic transmission of this organism is occurring. The planned investigations include: Survey the most common pet bird species for microsporidia. Document that Enc. hellem is shed from infected birds. Compare molecular sequences of the small subunit and ITS regions of rRNA genes from human and avian isolates of Enc. hellem. Establish experimental Enc. hellem infetions with human and avian isolates in SPF peach-faced lovebirds.